Process for pulling cables into conduits

Abstract

A method for reducing the friction between a conduit and a cable while the latter is pulled into the conduit consists of locating a layer of balls on the surface of the conduit or cable before laying. The balls have a diameter much lower than that of the cable, typically of the 0.1 to 1 mm range. The balls may be adhered to the cable as it progresses into the conduit, using for instance electrostatic forces. The balls may as well be blown into the conduit to form a carpet before the cable is forced into the tube. In both cases, friction is reduced whatever the angular portion of the conduit which is contacted by the cable during pulling.

We claim: 
     
       1. A method of locating a cable in a tubular conduit, including the steps of: forming a layer of balls having diameters substantially lower than the cable diameter and adhering to the inner surface of said tubular conduit, throughout the surface of the conduit by blowing an air flow in which said balls are in suspension along said conduit under conditions selected to distribute said balls throughout the length of said conduit; and pulling the cable along said conduit on said layer. 
     
     
       2. A method of locating an optical cable having an envelope of a predetermined diameter in a section of tubular conduit of dielectric material, comprising the steps of: blowing a flow of gas in which balls of dielectric material less hard than the materials of the envelope and conduit and of diameter of from 0.1 to 1 mm are suspended along said section from an end thereof until a field of said balls is formed on and adhered electrostatically to substantially the whole surface and throughout the length of said section; and pulling said cable along said section after said field has been completed. 
     
     
       3. A method according to claim 1, wherein said air flow is blown under a pressure which is progressively decreased as said field is formed beginning from the far end of the conduit. 
     
     
       4. A method according to claim 1, or 2, wherein said balls are of a material selected from the group consisting of polyamide, polyester and polyethylene material. 
     
     
       5. A method according to claim 1, wherein said balls have diameters selected in the range of from 0.1 mm to 1 mm and are of different diameters within said range. 
     
     
       6. A method according to claim 1, wherein a mist is injected into said tubular conduit for sticking said balls on the surface of said tubular conduit.